Cytoenzymology is the study of cellular enzyme function. Historically, the study of enzymatic activity of cells was pursued using cytosols. However, new reagents have been developed which are used to study enzymatic activity inside metabolically active whole cells. These new reagents have enabled cytoenzymology to advance to the stage where functional cell assays are possible to diagnose diseases and monitor therapeutic progress of such diseases by cytological examination under a microscope or by a flow cytometer. The new reagents that have been developed are synthetic fluorogenic substrate reagents that are available to measure enzyme activity inside the cellular structure. Examples of such fluorogenic substrate reagents are CELLPROBE reagents sold by Coulter Corporation, Miami, Fla. A further description of these new reagents are described in co-pending U.S. Pat. No. 5,776,720.
To determine the efficacy of a fluorogenic substrate reagent in the measurement of specific cellular enzyme activity, it is necessary to establish the efficacy of the reagent by an independent biological control material. The biological control material, also known as a cell control, is essential for determining the accuracy and precision of clinical and cytoenzymology assays. The cell control is needed to insure reliability and accuracy of test results and methods, and to insure reproducibility through time and from laboratory to laboratory. In addition, some state and federal regulations, which govern such assays, often require the use of a cell control in order to demonstrate that equipment is performing properly. The cell control should be stable and similar in nature to the sample under investigation.
U.S. Pat. No. 5,059,518 discloses a cell control, CYTO-TROL.RTM. made by Coulter Corporation, which consists of normal human cells that have been lyophilized in a hypertonic, trehalose containing media. The product is used as an antigen control in flow cytometry. The product is made from a depleted preparation of leukocytes wherein the lymphocytes are the only remaining white blood cells. However, this product does not retain enzymatic activity characteristic of normal human cells.